This invention relates to a power inlet arrangement for providing power to the electrical system of a building, such as power supplied by a standby generator.
Portable generators may be used in certain situations to feed electrical power to residential and commercial load circuits during a utility power outage. These systems frequently include a power inlet box adapted for interconnection with the generator. The power inlet box is typically mounted to the exterior of a building. The power inlet box is connected to a transfer switching mechanism which continues the electrical path through circuit breakers associated with the transfer switching mechanism, to supply power to certain selected circuits of the load center as determined by the transfer switching mechanism circuit breakers. The circuits of the transfer switching mechanism are wired to selected circuits of the load center, through wiring housed within a conduit extending between the load center and the transfer switching mechanism.
The present invention relates to a power transfer switching mechanism such as is disclosed in application Ser. No. 09/062,257, filed Apr. 17, 1998, the disclosure of which is hereby incorporated by reference. The ""257 application discloses a power input terminal arrangement in the power transfer switching mechanism in combination with a removable cover for preventing access to the power input terminal arrangement. The cover is provided with a power input structure, such as a socket or receptacle, connected to the terminal assembly for selectively receiving a plug connector electrically interconnected with a source of auxiliary power such as a generator. The power transfer switching mechanism in the ""257 application provides a selective connection between the remote power inlet box and the switches of the switching mechanism.
While the above-described transfer switching mechanisms provide extremely convenient and simple arrangements for establishing direct, hardwired and selective connections with the power inlet box, it is sometimes desirable to provide a power transfer switching mechanism having a power input meter arrangement in its front-panel. With this modification, it is possible to monitor the amount of power provided by a generator during a power outage, so as to prevent overloading of and subsequent damage to the generator or to the building electrical system. Although the broad concept of integrally providing power input meters on a power transfer switching mechanism is well known, it is desirable to modify the power transfer switching mechanisms described in the aforementioned co-pending patent applications to provide an optional meter arrangement in a cover which is selectively engageable with the cabinet of the switching mechanism.
One form of a power input meter arrangement for use in connection with a power transfer switching mechanism is disclosed in Flegel U.S. Pat. No. 6,107,701 issued Aug. 22, 2000, the disclosure of which is hereby incorporated by reference. The ""701 patent discloses a meter arrangement which is incorporated into the power supply from the remote power inlet box to the power input terminal arrangement of the power transfer switching mechanism. The system disclosed in the ""701 patent provides a highly satisfactory system for selectively providing a power input meter arrangement in a power transfer switching mechanism, but requires a number of connections in order to interconnect the power input meters.
It is an object of the present invention to provide a transfer switching mechanism having a removable access cover provided with a power input meter arrangement for measuring input power to the transfer switching mechanism from a generator or from a power inlet connected with the generator. It is a further object of the present invention to provide a power input meter arrangement for use in a transfer switching mechanism, which eliminates the numerous connections involved in the prior art system. Another object of the present invention is to provide a transfer switching mechanism which is simple to install and which operates generally similarly to prior art transfer switching mechanisms. It is also an object of the present invention to provide a method for constructing a power transfer device having a power input meter arrangement for monitoring power supplied by a generator so as to prevent overloading thereof.
The invention contemplates an improvement in a power transfer arrangement for supplying power from a generator to the electrical system of a building. The power transfer arrangement includes a power inlet arrangement for interconnection with the generator for receiving power therefrom, and a power transfer device separate from the power inlet arrangement adapted for interconnection with the building electrical system. The invention resides in a power input indicating structure for selectively displaying the amount of power provided by the generator. The power transfer device includes a cabinet having a front panel to which is mounted a set of switches for controlling the supply of power from the power transfer device to the building electrical system. The power transfer device further includes a compartment defined by the cabinet at a location spaced from the set of switches. The cabinet defines an opening providing access to the compartment. The cover is positionable over the opening and removably engageable with the cabinet for selectively closing the opening for preventing access to the compartment. The power input indicating structure is fixed to the cover. The power input indicating structure includes at least one meter having a block-like rear portion and a convexly-shaped forward portion projecting through a vertically extending wall of the cover. The forward portion includes a transparent window having a support member for mounting a wattage scale visible through the window, and an indicator mounted for movement along the scale in response to the supplying of power from the generator.
The power input indicating structure is preferably in the form of one or more watt meters mounted to the cover. A current transformer input arrangement is interconnected with each watt meter. Each current transformer input arrangement includes a current transformer coil defining an opening through which a power input wire extends. The current transformer coil is located within the compartment defined by the cabinet, and the power input wire extends between the power inlet arrangement and the switches of the power transfer device, for supplying power to the power transfer device from the generator. In a known manner, the current transformer coil cooperates with the meter to form an electrical circuit. Current in the power input wire induces a corresponding current in the current transformer coil, which acts on the watt meter to output a reading indicative of power supplied to the power transfer device. In this manner, a power input meter arrangement can be provided for the power transfer device without the need for making direct connections of the power input meter in the power supply path.
The invention further contemplates an improvement in a power transfer device adapted for interconnection with the electrical system of a building and including a cabinet. The invention is in the form of a compartment associated with the cabinet and a cover removably connected to the cabinet for alternately preventing and permitting access to the compartment. The cover is provided with a meter arrangement with a current transformer input arrangement, to selectively measure levels of power provided from a source of auxiliary power connected to the power transfer device.
The invention also relates to a method for constructing a power transfer device for supplying power to the electrical system of a building from a generator in electrical communication with a separate power inlet arrangement. The method includes the step of providing a cabinet having a compartment and a plurality of switches interconnected with power supply wires extending through the compartment, for controlling the supply of power from the power transfer device to the building electrical system; providing a first cover member adapted for removable engagement with the cabinet over the compartment for selectively enclosing the power input terminal arrangement; providing a second cover member having a power input meter arrangement with a current transformer input having an opening, which is adapted for removable engagement with the cabinet over the compartment for selectively enclosing the compartment; and mounting either the first cover member or the second cover member to the cabinet over the compartment. The step of mounting the second cover member includes passing the power supply wires through the opening defined by the current transformer input, for providing a current in the current transformer indicative of power supplied to the power transfer device, for providing a visual output from the power input meter arrangement.